Ask a makefile to print a variable value

Question

I have some generated GNUmakefiles from which I need to extract the value of a variable.

Is there an easy way to see the value of a variable without modifying the makefiles ?

FYI, the variables contain the path of some include files necessary for the emacs c-macro-expand function.

I work in a MegaCorp where it's difficult to modify anything. The makefiles are generated, I would have to modify the engine which create makefiles, and that seems very difficult. — BenjaminB
– BenjaminB, Commented Jan 7, 2013 at 7:11
You have my sympathy. MegaCorps and code generators have the same fault: layers of inflexible heirarchy that make change difficult. — Beta
– Beta, Commented Jan 7, 2013 at 16:26

Community · Accepted Answer · 2017-05-23 10:29:01Z

You could create a wrapper makefile, which includes necessary GNUmakefiles and prints the variable. For example, create wrapper.mk with the content

include GNUmakefile $(info $(value VAR_NAME))

and then invoke Make with -n flag (see @jeberle's answer):

make -f wrapper.mk -n # will print the variable value to stdout

jeberle · Accepted Answer · 2013-01-04 20:22:35Z

3

You could do:

$ make -n -p | grep VAR

to pick out the value

the flags are:

-n # don't really make -p # print database

answered Jan 4, 2013 at 20:22

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2 Comments

It does not evaluate the value of the variables, so it prints something like : INCFLAGS=$(MYINCFLAGS) -I...

You can grep for any name, e.g., grep MYINCFLAGS. If MYINCFLAGS is not set, it will evaluate to an empty string.